Can't fasten stuff directly onto a PCB that way. Only with wire holders. And shrink tube is considered as a potential failure node in safety circles. After a decade in some hard climate thinks might beging to fall off.
-- Regards, Joerg http://www.analogconsultants.com/
this:
Dang, just give in and use lacing cord. Explain to the young-uns that it is a cool new binding technique. ;-)
-- Rich Webb Norfolk, VA
this:
Yeah, I'll likely have them send me two boards for testing. Then I'll do the 2nd one with lacing cord and tell'em "This here board is how them real fellahs do it".
-- Regards, Joerg http://www.analogconsultants.com/
I can't understand why you're using a metal tie at corona-type voltages. =:-O
Thanks, Rich
Because it has to make darn sure it'll hold. The high voltage is only there in a fault situation. It will work, I've designed this stuff many times before and there's always metal in there somewhere. But in the past I got away with toroids which are very easy to mount. Not this time.
-- Regards, Joerg http://www.analogconsultants.com/
Just machine some Bakelite "doughnut holes" ;-) ...Jim Thompson
[On the Road, in New York]
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I love to cook with wine. Sometimes I even put it in the food.
Lacing's easy enough, but its pretty time consuming.
Much better than soldering banding is epoxy. Solder isnt exactly tough. You can use epoxy with other things too such as fibreglass.
NT
The metal ties he shows are a rugged version of a std plastic tie.
A low profile version has been used by the military connector guys for decades.
You pull it through and then you bend a 180 in the tail. The result is very low profile and fits under heat shrink easily. They are found with the backshells of many military type interconnects.
It would not be an agency issue, if it functioned. The VHB material is a listed adhesive system with UL under QOQW2.MH17478. You'd have to review it's suitability re temperature and flamability.
Lacing tape/cord has temperature, flamability and environmental issues as well.
You should also run some kind of testing with any potential metalic solution. HF transformers don't like close ferrous metal - even diamagnetic materials may induce heating effects you're not counting on. Anything forming a conductive loop may also have more than just a passive effect.
Working solutions in higher-powered equipment used adhesives and mechanical clamps with integral not-conductive elements.
RL
is:
I'd be reluctant (hah! No magnetic terminlogy joke implied!) to use a metal strap to hold a ferrite core to a PC board.
Electromagnetically making a single shorted turn (which is what your metal strap will be) may or may not be relevant to you.
Mechanical shock resistance (i.e. don't break the core if somebody drops the box) would be my big worry.
Not sure if you have a square rod, or a square transformer core, or a square ferrite ring, but look inside some consumer type equipment at how rods and transformers are attached to PCB's. I've seen everything from wax (e.g. old portable transistor radios with rods) to molded plastic holders (these seem *VERY* ideal to me in terms of both standoff and mechanical shock absorption) to plastic transformer housings being used.
Even with e.g. molded chokes you have to realize that the high density of the ferrite material requires a lot of mechanical thought with regards to mounting.
Tim.
I've never heard that; there are shrink-tube variants to protect buried splices that ought too last decades with no problem. If you kerf the PC board, heatshrink CAN fasten stuff to your PCB.
If other tapes aren't acceptable, and it's a longevity issue, I'd consider fiberglass tape as well.
They'd want endurance tests and that can get old. I'd rather not rely on glues here.
Sure, but there is a major advantage: Aerospace certifications already exist and that usually makes a very compelling case in front of a notified body.
That's what I'll have to try but IME it hasn't mattered too much. The loops go around the outside of the ferrite core, outside the magnetic loop. I have shielded such cores in the past where the shield was total, and cradled them closely. There was only some minor capacitive loading with toroids (expected) but not with multi-aperture cores.
No adhesives. I'd be ok with a (serious) non-conductive clamp but they don't seem to exist. Plastic tie-wrap are not so great because the can dry out and then snap. Too flimsy. I took apart an older machine earlier this year and at least half the tie-wraps had snapped and fallen onto the bottom panel, leaving some harnesses dangling a bit.
-- Regards, Joerg http://www.analogconsultants.com/
Usually not, at least I've never seen that.
Got to muffle that anyhow because the board can flex a bit upon impact. I was planning on neoprene or stuff like that. Between strap, board and core.
It's a double-hole core but a big old fat one. Rather squarish, about
1.2" by 1.2" and 0.6" thick. The windings run only through the holes, not along the outside of the core.Yes, ferrite is iffy. That's why I plan to cushion it with something like neoprene. You can buy it in sheets everywhere and cut it with scissors.
-- Regards, Joerg http://www.analogconsultants.com/
That only works if at the corner of the board. You'd have to slit into it twice, creating a long tongue -> potential fractures, because ferrite weighs a bit.
Yes, shrink tube can last a decade. But this sort of stuff sometimes needs 2-3 decades.
That still relies on glue. If it dries up the tape will unravel and the ferrite eventually falls off.
-- Regards, Joerg http://www.analogconsultants.com/
those lock with a ball bearing that wedges in the ramp. they will hold forever. there's no need to fold the end back.
they're fairly stiff so tightening one on ferrite with square edges is asking to chip the edges off.
Thanks, that's good to know.
I plan to protect them with neoprene. Need that anyhow for buffer because the steel straps don't have much compliance.
But how stiff can they really be if the thickness of the 304 stainless steel is only .010"? I have shaped a hose clamps around square objects with my fingers and those are much thicker.
-- Regards, Joerg http://www.analogconsultants.com/
this:
snip
weren't you going to wrap it in neopren anyway?
if you have access to a mill or even just a tablesaw and a drill press it wouldn't take many minutes to cut a 1.2"x0.6" slot in a piece of
20mm acetal or something like that, cut it into 1.2" long pieces and drill some holes for screws-Lasse
this:
Yes, but you'd still have to apply tension and solder joints really do not like that at all. Solder has a tendency to creep under pressure or tension.
Sure, but my clients usually prefer a part number and a price over a custom part that needs SOPs, ECOs and all that "fun stuff" :-)
Seriously, I've already got two (unavoidable) custom parts on there. With the whole bureaucratic paper trail.
-- Regards, Joerg http://www.analogconsultants.com/
ran
Found this:
or
that
scissors.
If i thought the product was made in a size small enough for your needs i would suggest SS banding like is sometimes used to attach signs and other equipment to signal poles and the like. It is a lot like steel shipping strapping. There are thermo welded plastic versions also.
?-)
Since you need to buffer it somehow from shock have a look at pro-seal or other FAA (since you talked about lacing cord) approved sealants. This stuff will stick to fiberglass and metal. It's messy (I know from first hand experience) but that ferrite is not going anywhere once this stuff cures. Temp range is -65F to +275F
Just a thought....
or
-- Joe Chisolm
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